I. Field of the Invention
This invention relates generally to the analysis of materials, and more particularly to a new arrangement for the end portion of a light guide which directs light to to photospectormeter from a liquid sample located in a cuvette. The present invention is particularly useful in automated chemistry analyzers which are employed for determining the presence and levels of one or more selected constituents in relatively small biological liquid samples.
II. Description of the Prior Art
Numerous automated clinical analyzers are known and widely used in hospital clinical laboratories. An example of such an analyzer is the multi-channel type analyzer.
A multi-channel analyzer is one in which a series of different tests are performed simulataneously by the analyzer, and in parallel with one another. Such an analyzer can be best visualized as a series of batch analyzers operating in parallel wherein each channel performs a single analysis test. The multi-channel type analyzer generally utilizes a liquid reagent to react with the particular constituent being tested in the sample and a photo-optical system to read the optical absorbence of the sample which corresponds to the level of the constituent in the sample.
Although this type of automated analyzer has received wide acceptance in the clinical laboratory, certain drawbacks are associated with its use. For example, although the multi-channel type analyzer is reliable due to its simplicity, cost effective for large number of samples and has a relatively high test throughout rate, it is limited in the sense that it can only be effectively utilized to perform a single constituent analysis at a time on a relatively large number of samples. In addition, such analyzers are not capable of performing emergency "stat" tests due to their relatively long and complex set up time and their inherent inability to economically analyze a single test sample. Thus, the efficiency of this type of system is not the best.
A further significant disadvantage found is that although tests can be simultaneously performed for multiple constituents on the same sample, generally all of these tests must be performed for every sample whether desired or not. This results in waste of both sample material and the reagents used in the unnecessary tests. Furthermore, due to the fact that multiple discrete and dedicated channels are utilized in such an instrument, there is significant duplication of numerous components which adds to the complexity and expense of the overall instrument.
An automated single track clinical analyzer which avoids the above-described drawbacks is described in commonly owned U.S. Pat. No. 4,528,157 entitled, "Automated Analysis Instrument System", the disclosure of which is hereby incorporated by reference in its entirety. Furthermore, by using a unique photo-optical system, described in commonly owned U.S. Pat. No. 4,528,159 entitled, "Multichannel Spectrophotometer", the disclosure of which is hereby incorporated by reference in its entirety, greater flexibility of analysis at each analysis station is achieved. This is because this photo-optical system employs fiber optic bundles or similar light guides to transmit variable wavelengths of light to each analysis station from a single light source.
The single track analyzer utilizes a disposable cuvette belt formed from thin plastic film defining a series of discrete reaction compartments (cuvettes) which are transported in line through the instrument. Such a cuvette belt is described in commonly owned, abandoned U.S. patent application Ser. No. 284,842, filed July 20, 1981 entitled, "Cuvette System for Automated Chemical Analyzers". This belt provides hanbling flexibility and avoids the cross-contamination associated with flow-through cuvettes as well as avoiding the washing required for reusable cuvettes.
In employing a photo-optical system for critical analysis work, it is very important that there be substantially no interference with the path of light that is directed from the sample being analyzed through a light tube which in turn directs the light to a photospectrometer. Any interference with this light path can effect the accuracy of the analysis, and lead to incorrect results. However, it is typical of many of the prior art analysis systems that a good deal of "noise" is received from the light signal sent to a photospectrometer from a sample being analyzed. This noise causes a scattering of the test results. Also, the test results tend to "float". When using a series of photospectrometers in an analysis system there is a tendency to avoid focussing of the light signal to the photospectrometers thereby introducing tracing errors from one analyzer to another analyzer. The end result of all of these problems is that the level of accuracy of the analysis is reduced.